The mind is an inner sky; the passions, cares, and tangled impressions are cloud-cover, mist, foul weather; philosophical work is what disperses the clouds and returns the sky to clarity. The Greek verb ἀπαιθριάσαι is derived from αἰθρία ("clear sky," "fair weather") with the prefix ἀπο- (removal, separation): literally "to clear up the weather," "to wipe down to the bright sky." The image presupposes not the construction of something new but a return to a natural state: the sky is clear of itself; the clouds are accretions. The mind, in its healthy state, is clear; only assents to false impressions cloud it.

Med. 2.4: ᾧ ἐὰν εἰς τὸ ἀπαιθριάσαι μὴ χρήσῃ, οἰχήσεται ("if you do not use [your time] for the clearing of the inner sky, it will be gone"). The verb is rare; in Marcus it occurs only here, but the image recurs: Med. 4.3 (the inner refuge — "no more quiet and unperturbed retreat than one's own soul"); 5.34 ("it is yours, like the sun's, to shine"); 8.5 ("what hinders my mind from being shrewd, friendly, free of passion?"); 11.16 (the light of the soul as weather). The Greek background: Plat. Phaedr. 247c (the soul's vision of "the bright sky" of true being); the philosophical tradition of serenity as clarity (ἀταραξία in Epicurus, ἀπάθεια in the Stoics).

In 02-04 the image does double work. (1) Aesthetic — this is a rare positive metaphor in Marcus (most of his images are deprecatory: the body as a weaving of sinews, the person as a puppet on strings). The clearing of the sky points to that for which the whole ascetic exercise exists: an inner state that answers to the cosmic αἰθρία. (2) Argumentative — it specifies the goal for the use of the time allotted (the limit of one's time): not "to manage to read the books," but "to manage to clear the mind." Linked to the doctrine of DOGMAself-is-hegemonikon: the clear sky of the mind is the "I" fully present.